Field of the Invention
The present invention relates to a cutting apparatus including a cutting blade and also to a wafer cutting method.
Description of the Related Art
A plurality of devices such as ICs and LSIs are formed on the front side of a wafer so as to be separated by a plurality of division lines (streets). The wafer thus having the devices is divided along the division lines into individual device chips by using a cutting apparatus including a rotatable cutting blade (see Japanese Patent Laid-open No. 2001-144034, for example). The device chips are used in various electronic equipment. To increase the speed of processing by the ICs and LSIs, the resistance or capacitance of wiring in each device must be reduced. This is due to the fact that a signal delay having a large effect on a processing speed is determined by the product of resistance and capacitance. In a wafer put in a practical use, low-permittivity insulator films and metal foils are alternately stacked to form a multilayer structure on the upper surface of a semiconductor substrate such as a silicon substrate. Each low-permittivity insulator film is formed from an inorganic film such as SiOF film (fluorine-doped silicon oxide film) and BSG film or an organic film such as a polymer film of polyimide or parylene. Each metal foil is formed of copper, aluminum, etc. The multilayer structure formed on the upper surface of the semiconductor substrate forming this wafer is also partitioned by a plurality of crossing division lines to form a plurality of devices.
Each low-permittivity insulator film is called a low-k film because it has a low relative permittivity k. The stacked low-k films are formed not only on the surface of each device, but also on the surface of each street. Since the number of interlayer spacings in the stacked low-k films is large, the stacked low-k films are very brittle and they are prone to separate from the surface of each device like mica. Accordingly, when each street is cut by using a cutting blade, there is a possibility of delamination of the low-k films in the range from each street to the adjacent devices due to the ductility of the metal forming the metal foils, causing a remarkable reduction in quality of each device. As a method for preventing such delamination reaching the adjacent devices, there has been proposed a method including the steps of applying a laser beam along each street to thereby remove the low-k films present on each street and next cutting a semiconductor substrate exposed along each street by using a cutting blade (see Japanese Patent Laid-open No. 2008-4822, for example).